Cell adhesion complexes are a bio-medically important class of multi-protein assemblies. They are involved in sensing Interactions between cells and their external environment, and then initiating and regulating intracellular signals that control cell migration, cell shape and functional organization, proliferation and survival, and gene expression. They are evolutionarily old, critical for normal development and homeostasis, and are defective in genetic diseases and cancer. Currently, there is a lack of a concerted effort to integrate available genomic (evolutionary) and structural information to rigorously solve the hierarchical structural organization of these multi-protein complexes at the atomic, meso and macro scale. A further barrier to progress is the availability of large amounts of purified proteins for multi-protein complex reconstitution since classical approaches are not feasible due to the unstable nature of complex protein assemblies. The Consortium will leverage high-throughput expression and structures of large sets of target families of proteins and signaling networks to understand the structural and functional organization of both cell-cell and cell-ECM adhesion complexes. The Consortium will integrate expertise in structural biology (X-ray crystallography, electron microscopy of in situ complexes), biochemistry and cell biology (in vitro reconstitution), chemistry and live cell imaging (in situ bio-sensors and caged proteins) by: Specific Aim 1: Define multi-protein interactions, stoichiometries and affinities in solution (Liddington, Weis). Specific Aim 2: Reconstitute multi-protein complexes on biological membranes (Ginsberg, Nelson). Specific Aim 3: Define structures of multi-protein complexes in situ, at a physiological environment (Hanein, Volkmann). Specific Aim 4: Analyze dynamic protein-protein interactions and assembly in live cells (Hahn).